1. Field of the Invention
The present invention relates to a method of manufacturing n-doped graphene and an electrical component, and to graphene and an electrical component thereby. More particularly, the present invention relates to a method of manufacturing n-doped graphene and an electrical component using ammonium fluoride (NH4F), and to graphene and an electrical component thereby.
2. Description of the Related Art
Recently, attempts are being made to develop a variety of materials using nanotechnology able to outperform properties of conventional materials. A typical example of such a material is graphene. Graphene is a material having a two dimensional planar structure of carbon atoms which are bonded to each other, and has diverse advantages including high charge mobility, superior mechanical strength, transparency, etc. It may be prepared using currently available semiconductor processing techniques and is thus gaining attention as a next-generation material.
An electronic material to which graphene is applied is typically exemplified by a transistor channel having a high operating speed thanks to high charge mobility. Furthermore, when it is applied to a field effect transistor (FET), the operating frequency may be drastically improved. However, forming an electrical component such as FET using graphene as above essentially requires a doping process of graphene with electrons or holes. As such, hole doping, namely, p-doping occurs naturally in the course of preparation of graphene, thus obviating an additional process, but electron doping, namely, n-doping needs an additional process.
N-doping processes developed to date may be classified into growth process and post-growth process types. A typical example of the growth process type is chemical vapor deposition (CVD). This process may be applied to manufacture pure graphene, but may be used in such a manner that a gas (nitrogen or ammonia gas) containing a nitrogen atom may be added to a gas feed, so that the nitrogen atom is injected to bonds between carbon atoms in coincidence with growing graphene. In the case where FET is made using n-type graphene thus grown, charge mobility is measured to be about 200˜450 cm2/V sec based on a field effect.
Examples of the post-growth process type include a thermal treatment process and a plasma treatment process, and the thermal treatment process may be subdivided into a process using gas and a process using a high-temperature solution. The process using gas is performed in such a manner that oxidized graphene (graphene oxide) is placed in a gas chamber filled with ammonia gas, and then reduced through thermal treatment at high temperature and simultaneously n-doping is executed. Similarly, the process using a solution implements to reduction and doping while heating oxidized graphene up to about 200° C. in an ammonia aqueous solution. However, the above thermal treatment process is problematic because oxidized graphene, which is mainly used, is unlikely to return to graphene having original high charge mobility even when reduced.
The plasma treatment process is performed by generating plasma in a gas chamber filled with ammonium or nitrogen gas and then bringing such plasma into immediate contact with graphene to thus inject a nitrogen atom. This method is advantageous because large-area high-quality graphene grown using CVD may be subjected to electron doping, but is disadvantageous because a plurality of carbon-oxygen bonds in graphene may be generated as by-product after plasma treatment, remarkably degrading electrical properties of graphene.
Moreover, Korean Patent Application Publication No. 10-2012-0099910 (published on Sep. 12, 2012) discloses an n-doping process of graphene comprising reacting a reactive gas containing a carbon source and heat on a substrate 10 to grow graphene 20 on the substrate 10, and doping such graphene 20 by use of a vapor or a doping solution 30 containing an n-type dopant. FIG. 1 illustrates an n-doping process of graphene 20 using a doping solution 30 according to the above conventional technique. However, even when such a method is used, the above conventional problems are difficult to fundamentally solve.
Although the aforementioned conventional methods enable n-doping of graphene, electrical properties of graphene including charge mobility may be remarkably degraded. Therefore, the demand for n-doping methods of graphene while maintaining or improving electrical properties of graphene is continuously increasing but appropriate solutions therefor have not yet been proposed.